Front pieces of control and regulation electronic instruments and relevant regulation knobs



FIG. 1 is a perspective view of front pieces of control and regulation electronic instruments and relevant regulation knobs showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view. 

The ornamental design for front pieces of control and regulation electronic instruments and relevant regulation knobs, as shown. 